# User options
use_precompile <- FALSE
use_gpu <- FALSE

# For Windows, the package will be built with Visual Studio
# unless you set one of these to TRUE
use_mingw <- FALSE
use_msys2 <- FALSE

if (use_mingw && use_msys2) {
  stop("Cannot use both MinGW and MSYS2. Please choose only one.")
}

if (.Machine$sizeof.pointer != 8L) {
  stop("LightGBM only supports 64-bit R, please check the version of R and Rtools.")
}

R_int_UUID <- .Internal(internalsID())
R_ver <- as.double(R.Version()$major) + as.double(R.Version()$minor) / 10.0

if (!(R_int_UUID == "0310d4b8-ccb1-4bb8-ba94-d36a55f60262"
    || R_int_UUID == "2fdf6c18-697a-4ba7-b8ef-11c0d92f1327")) {
  warning("Warning: unmatched R_INTERNALS_UUID, may not run normally.")
}

# system() will not raise an R exception if the process called
# fails. Wrapping it here to get that behavior.
#
# system() introduces a lot of overhead, at least on Windows,
# so trying processx if it is available
.run_shell_command <- function(cmd, args, strict = TRUE) {
    on_windows <- .Platform$OS.type == "windows"
    has_processx <- suppressMessages({
      suppressWarnings({
        require("processx")  # nolint
      })
    })
    if (has_processx && on_windows) {
      result <- processx::run(
        command = cmd
        , args = args
        , windows_verbatim_args = TRUE
        , error_on_status = FALSE
        , echo = TRUE
      )
      exit_code <- result$status
    } else {
      if (on_windows) {
        message(paste0(
          "Using system() to run shell commands. Installing "
          , "'processx' with install.packages('processx') might "
          , "make this faster."
        ))
      }
      cmd <- paste0(cmd, " ", paste0(args, collapse = " "))
      exit_code <- system(cmd)
    }

    if (exit_code != 0L && isTRUE(strict)) {
        stop(paste0("Command failed with exit code: ", exit_code))
    }
    return(invisible(exit_code))
}

# try to generate Visual Studio build files
.generate_vs_makefiles <- function(cmake_args) {
  vs_versions <- c(
    "Visual Studio 16 2019"
    , "Visual Studio 15 2017"
    , "Visual Studio 14 2015"
  )
  working_vs_version <- NULL
  for (vs_version in vs_versions) {
    message(sprintf("Trying '%s'", vs_version))
    # if the build directory is not empty, clean it
    if (file.exists("CMakeCache.txt")) {
      file.remove("CMakeCache.txt")
    }
    vs_cmake_args <- c(
      cmake_args
      , "-G"
      , shQuote(vs_version)
      , "-A"
      , "x64"
    )
    exit_code <- .run_shell_command("cmake", c(vs_cmake_args, ".."), strict = FALSE)
    if (exit_code == 0L) {
      message(sprintf("Successfully created build files for '%s'", vs_version))
      return(invisible(TRUE))
    }

  }
  return(invisible(FALSE))
}

# Move in CMakeLists.txt
write_succeeded <- file.copy(
  "../inst/bin/CMakeLists.txt"
  , "CMakeLists.txt"
  , overwrite = TRUE
)
if (!write_succeeded) {
  stop("Copying CMakeLists.txt failed")
}

# Get some paths
source_dir <- file.path(R_PACKAGE_SOURCE, "src", fsep = "/")
build_dir <- file.path(source_dir, "build", fsep = "/")

# Check for precompilation
if (!use_precompile) {

  # Prepare building package
  dir.create(
    build_dir
    , recursive = TRUE
    , showWarnings = FALSE
  )
  setwd(build_dir)

  use_visual_studio <- !(use_mingw || use_msys2)

  # If using MSVC to build, pull in the script used
  # to create R.def from R.dll
  if (WINDOWS && use_visual_studio) {
    write_succeeded <- file.copy(
      "../../inst/make-r-def.R"
      , file.path(build_dir, "make-r-def.R")
      , overwrite = TRUE
    )
    if (!write_succeeded) {
      stop("Copying make-r-def.R failed")
    }
  }

  # Prepare installation steps
  cmake_args <- NULL
  build_cmd <- "make"
  build_args <- "_lightgbm"
  lib_folder <- file.path(source_dir, fsep = "/")

  WINDOWS_BUILD_TOOLS <- list(
    "MinGW" = c(
      build_tool = "mingw32-make.exe"
      , makefile_generator = "MinGW Makefiles"
    )
    , "MSYS2" = c(
      build_tool = "make.exe"
      , makefile_generator = "MSYS Makefiles"
    )
  )

  if (use_mingw) {
    windows_toolchain <- "MinGW"
  } else if (use_msys2) {
    windows_toolchain <- "MSYS2"
  } else {
    # Rtools 4.0 moved from MinGW to MSYS toolchain. If user tries
    # Visual Studio install but that fails, fall back to the toolchain
    # supported in Rtools
    if (R_ver >= 4.0) {
      windows_toolchain <- "MSYS2"
    } else {
      windows_toolchain <- "MinGW"
    }
  }
  windows_build_tool <- WINDOWS_BUILD_TOOLS[[windows_toolchain]][["build_tool"]]
  windows_makefile_generator <- WINDOWS_BUILD_TOOLS[[windows_toolchain]][["makefile_generator"]]

  if (use_gpu) {
    cmake_args <- c(cmake_args, "-DUSE_GPU=ON")
  }
  if (R_ver >= 3.5) {
    cmake_args <- c(cmake_args, "-DUSE_R35=ON")
  }
  cmake_args <- c(cmake_args, "-DBUILD_FOR_R=ON")

  # Pass in R version, used to help find R executable for linking
  R_version_string <- paste(
    R.Version()[["major"]]
    , R.Version()[["minor"]]
    , sep = "."
  )
  r_version_arg <- sprintf("-DCMAKE_R_VERSION='%s'", R_version_string)
  cmake_args <- c(cmake_args, r_version_arg)

  # the checks below might already run `cmake -G`. If they do, set this flag
  # to TRUE to avoid re-running it later
  makefiles_already_generated <- FALSE

  # Check if Windows installation (for gcc vs Visual Studio)
  if (WINDOWS) {
    if (!use_visual_studio) {
      message(sprintf("Trying to build with %s", windows_toolchain))
      # Must build twice for Windows due sh.exe in Rtools
      cmake_args <- c(cmake_args, "-G", shQuote(windows_makefile_generator))
      .run_shell_command("cmake", c(cmake_args, ".."), strict = FALSE)
      build_cmd <- windows_build_tool
      build_args <- "_lightgbm"
    } else {
      visual_studio_succeeded <- .generate_vs_makefiles(cmake_args)
      if (!isTRUE(visual_studio_succeeded)) {
        warning(sprintf("Building with Visual Studio failed. Attempting with %s", windows_toolchain))
        # Must build twice for Windows due sh.exe in Rtools
        cmake_args <- c(cmake_args, "-G", shQuote(windows_makefile_generator))
        .run_shell_command("cmake", c(cmake_args, ".."), strict = FALSE)
        build_cmd <- windows_build_tool
        build_args <- "_lightgbm"
      } else {
        build_cmd <- "cmake"
        build_args <- c("--build", ".", "--target", "_lightgbm", "--config", "Release")
        lib_folder <- file.path(source_dir, "Release", fsep = "/")
        makefiles_already_generated <- TRUE
      }
    }
  } else {
      .run_shell_command("cmake", c(cmake_args, ".."))
      makefiles_already_generated <- TRUE
  }

  # generate build files
  if (!makefiles_already_generated) {
    .run_shell_command("cmake", c(cmake_args, ".."))
  }

  # R CMD check complains about the .NOTPARALLEL directive created in the cmake
  # Makefile. We don't need it here anyway since targets are built serially, so trying
  # to remove it with this hack
  generated_makefile <- file.path(
    build_dir
    , "Makefile"
  )
  if (file.exists(generated_makefile)) {
    makefile_txt <- readLines(
      con = generated_makefile
    )
    makefile_txt <- gsub(
      pattern = ".*NOTPARALLEL.*"
      , replacement = ""
      , x = makefile_txt
    )
    writeLines(
      text = makefile_txt
      , con = generated_makefile
      , sep = "\n"
    )
  }

  # build the library
  message("Building lib_lightgbm")
  .run_shell_command(build_cmd, build_args)
  src <- file.path(lib_folder, paste0("lib_lightgbm", SHLIB_EXT), fsep = "/")

} else {

  # Has precompiled package
  lib_folder <- file.path(R_PACKAGE_SOURCE, "../", fsep = "/")
  shared_object_file <- file.path(
    lib_folder
    , paste0("lib_lightgbm", SHLIB_EXT)
    , fsep = "/"
  )
  release_file <- file.path(
    lib_folder
    , paste0("Release/lib_lightgbm", SHLIB_EXT)
    , fsep = "/"
  )
  windows_shared_object_file <- file.path(
    lib_folder
    , paste0("/windows/x64/DLL/lib_lightgbm", SHLIB_EXT)
    , fsep = "/"
  )
  if (file.exists(shared_object_file)) {
    src <- shared_object_file
  } else if (file.exists(release_file)) {
    src <- release_file
  } else {
    # Expected result: installation will fail if it is not here or any other
    src <- windows_shared_object_file
  }
}

# Packages with install.libs.R need to copy some artifacts into the
# expected places in the package structure.
# see https://cran.r-project.org/doc/manuals/r-devel/R-exts.html#Package-subdirectories,
# especially the paragraph on install.libs.R
dest <- file.path(R_PACKAGE_DIR, paste0("libs", R_ARCH), fsep = "/")
dir.create(dest, recursive = TRUE, showWarnings = FALSE)
if (file.exists(src)) {
  message(paste0("Found library file: ", src, " to move to ", dest))
  file.copy(src, dest, overwrite = TRUE)

  symbols_file <- file.path(source_dir, "symbols.rds")
  if (file.exists(symbols_file)) {
    file.copy(symbols_file, dest, overwrite = TRUE)
  }

} else {
  stop(paste0("Cannot find lib_lightgbm", SHLIB_EXT))
}

# clean up the "build" directory
if (dir.exists(build_dir)) {
  message("Removing 'build/' directory")
  unlink(
    x = build_dir
    , recursive = TRUE
    , force = TRUE
  )
}
